An international team of scientists has launched a high-altitude,
balloon-borne instrument from Antarctica to search for antimatter,
which is among the rarest and most elusive types of particles in the
Universe.

The team seeks to understand the origin of cosmic antimatter and to find
evidence for the existence of Hawking radiation from "evaporating" black
holes, a theory proposed by Prof. Stephen Hawking of Cambridge University
in England.

The instrument, called BESS-Polar, launched successfully on December 13
from McMurdo Station, Antarctica, beneath a 40-million-cubic-foot
scientific balloon, as big as a football field. To maximize the
possibility of finding the antimatter predicted by Hawking, the team is
hoping for at least a 10-day flight, or once around the South Pole, in
a near-space environment above 99% of the atmosphere. The instrument is
now circling the Pole at an average altitude of 24 miles (39
kilometers).

"Our earlier, shorter flights from northern Canada have provided hints of
the signature of Hawking radiation," said Principal Investigator Prof.
Akira Yamamoto of Japan's High Energy Accelerator Research Organization
(KEK). "With a longer flight and a greater 'harvest' of antiprotons, we
might be able to show that Prof. Hawking is right."

BESS-Polar is collaboration among scientists at KEK, the University of
Tokyo, Kobe University, and the Institute of Space and Astronautical
Science of the Japan Aerospace Exploration Agency, along with NASA and
the University of Maryland, College Park. BESS stands for Balloon-borne
Experiment with a Superconducting Spectrometer.

Antimatter is made up of particles with equal but opposite characteristics
of the particles of matter we interact with everyday. For example,
protons have a positive charge, but antiprotons have a negative charge.
Antiprotons created in space bombard the Earth in the form of cosmic rays,
which are elementary particles traveling at near light speed. When matter
and antimatter collide, they annihilate, creating pure energy and no "ash".

The most basic form of the Big Bang theory predicts that equal amounts of
matter and antimatter were created. Somehow, matter dominated antimatter
in the initial moments following the Big Bang. One of the BESS-Polar
project's goals is to see if there is any evidence of antimatter domains
left over from the Big Bang. The apparent matter-antimatter asymmetry is
a fundamental puzzle in elementary particle physics and also in astronomy.

The study of lower-energy antiproton particles is particularly exciting,
Yamamoto said, because they might have been created by "evaporating" black
holes, a process called Hawking radiation not yet seen in nature. This
would be from primordial, microscopic black holes created just after the
Big Bang. Finding antiproton particles in an abundance and energy range
predicted by theory would serve as compelling evidence.

"The northern and southern polar regions are the best places to collect
low-energy antiprotons," said U.S. Principal Investigator Dr. John Mitchell
of NASA Goddard Space Flight Center, at McMurdo Station for the flight.
"The Earth's magnetic field protects us from antiprotons and other
cosmic-ray particles from space. The magnetic field funnels charged
particles toward the Earth's poles, so the concentration of lower-energy
cosmic rays entering into the Earth's atmosphere there is greater."

This is the first flight for BESS-Polar. Scientists have flown an earlier
version called BESS for daylong flights in northern Canada once a year
nearly every year from 1993 to 2002. That instrument collected millions
of cosmic rays and a few thousand low-energy antiprotons. But more are
needed for better analysis.

"We journeyed to the bottom of the world so that we could get a nice,
long flight," said Project Manager Prof. Tetsuya Yoshida of KEK. "Longer
flights mean better statistics."

Constant daylight in Antarctica means no day-to-night temperature
fluctuations on the balloon craft, which helps the balloon stay at a
constant altitude for longer. The BESS-Polar team hopes to collect
enough antiprotons to characterize their absolute intensity (number per
square meter per second per solid angle) among other the cosmic rays in
terms of energy.